mask problem

I am trying to create a fence by using a black and white jpeg as a mask on a plane where the white parts represents the metal fence.

If i understand correctly, blitz has to have r=0,b=0,g=0 ie totally black to be transparent. The problem is that i'm using photoshop to produce the black and white jpeg by using the multi-layer function. When i merge the layers together, photoshop seems to "blurr" the white parts with the black parts to create smooth blend. This means i have no control over what area i want "totally" black therefore i end up getting a very messy fence.

1. I wouldn't use a jpg as it's going to leave artifacts all over the place and spoil it, use a png.

2. 2D or 3D?

3. If 2D then you don't need to use black, use the maskcolor command and use something really obvious like magenta then it will be easy to see what's transparant and what isn't.

4. If 3D then use an alpha mask, this way you can have your smooth blend so the black bits are 100% transparant and greys are x% transparant, this way you'll end up with a nice smooth effect. You'll have to save your texture as a PNG or TGA with the alpha channel, then load it into blitz using the alpha flag.

Basically your problem is what you're doing in photoshop though, nothing to do with blitz per se, and I'm no expert in photoshop so I can't help you there... Sorry.